WEDNESDAY, April 2 (HealthDay News) — A topical cream appears to be a highly effective treatment for precancerous lesions on the vulva, Dutch researchers report.

Rather than directly targeting the disease itself, the cream works by helping the body's own immune system fight off the human papillomavirus (HPV) — which is often the root cause of the rare condition. The cream is currently used for precancerous skin lesions and superficial basal cell carcinoma, a highly treatable form of skin cancer.

"This is a disease that is normally treated by surgery, but that just takes away a lesion without getting at HPV, a common underlying root of the disease," said study author Dr. Manon van Seters, from the department of gynecology at Erasmus University Medical Center in Rotterdam. "So, you have a chance that the lesion will come back, time and time again. But we found that the cream is a much less invasive and friendly way to get good lasting results."

The study was expected to be published in the April 3 issue of the New England Journal of Medicine.

Seters stressed that the cream was tested only as a treatment for the precancerous disease — not vulvar cancer itself.

"And we don't believe it'll work in vulvar cancer itself, because the invasive cancer itself is not as much related to the HPV virus," she said.

Vulvar cancer is a relatively rare disease that typically develops slowly over many years, often preceded by precancerous changes occurring in a woman's outer genitalia, within the tissues surrounding the opening of the vagina.

According to the American Cancer Society, vulvar cancer accounts for just over half of 1 percent of all cancers among American women. The organization projects that almost 3,500 new cases will be diagnosed this year, while about 870 American women will die from the illness in the same timeframe.

One-third to half of all vulvar cancer cases are related to infection with HPV, which is the same virus responsible for nearly all instances of cervical cancer.

Depending on the severity of the disease, the cancer society noted that current treatment options range from laser surgery to invasive and often repeated surgery to remove all or part of the vulva. Groin lymph node removal, radiation and chemotherapy are additional options.

Seters and her team explored the potential for the cream treatment among 52 women already diagnosed with the precancerous condition.

All the women sought care at Erasmus or at a second facility in Amsterdam between 2001 and 2003, and all were over the age of 18, sexually active, and premenopausal. The majority had grade 3 disease, while none had a history of vulvar cancer.

Half were randomly assigned to receive 250 milligrams of imiquimod 5 percent, while the other half was given a placebo cream. The creams were applied to lesions in a thin layer twice a week for 16 weeks.

By the end of treatment, about four in five of the imiquimod patients experienced a reduction in lesion size of more than 25 percent. None of the placebo patients saw their lesions shrink to this degree.

Lesion reduction of more than 75 percent occurred in five imiquimod patients, and lesions completely disappeared in nine imiquimod patients. These women remained lesion-free one year later. Eight imiquimod patients were determined to be completely free of the disease both at treatment end and one year after.

As well, 15 imiquimod patients were found to be clear of HPV immediately following treatment, compared with just two placebo patients.

Even among those still battling the lesions post-treatment, almost 70 percent of the imiquimod patients saw their disease severity drop from grade 3 to grade 2. This was the case in only one placebo patient.

Imiquimod appeared to improve quality of life as well, as severe itching and pain was lower among treated patients than placebo patients both right after treatment and one year later.

Seters and her colleagues say they still must map out the exact mechanics behind the cream's impact, while exploring why some patients benefited while others did not. Nevertheless, they concluded that the cream should be considered the "first-choice treatment" for these lesions.

However, Debbie Saslow, director of breast and gynecologic cancer at the American Cancer Society in Atlanta, offered a word of caution.

"While it moves the field forward, and it's important and very exciting, they still need larger numbers than this to be able to tell women that this is the new standard of care," she said. "But, of course, if we can ultimately recommend a topical cream for 16 weeks instead of an invasive surgical or laser procedure, that's going to be a big advantage."